Buggy code:
@ JRubyClass ( name = "Exception" ) public class RubyException extends RubyObject { protected RubyException ( Ruby runtime , RubyClass rubyClass ) { } public RubyException ( Ruby runtime , RubyClass rubyClass , String message ) { } @ JRubyMethod ( optional = 2 , visibility = PRIVATE ) public IRubyObject initialize ( IRubyObject [ ] args , Block block ) { } @ JRubyMethod public IRubyObject backtrace ( ) { } @ JRubyMethod ( required = 1 ) public IRubyObject set_backtrace ( IRubyObject obj ) { } private void setBacktrace ( IRubyObject obj ) { if ( obj . isNil ( ) ) { backtrace = null ; } else if ( isArrayOfStrings ( obj ) ) { backtrace = obj ; } else if ( obj instanceof RubyString ) { backtrace = RubyArray . newArray ( getRuntime ( ) , obj ) ; } else { <START_BUG> throw getRuntime ( ) . newTypeError ( "backtrace<seq2seq4repair_space>must<seq2seq4repair_space>be<seq2seq4repair_space>Array<seq2seq4repair_space>of<seq2seq4repair_space>String<seq2seq4repair_space>or<seq2seq4repair_space>a<seq2seq4repair_space>single<seq2seq4repair_space>String" ) ; <END_BUG> } } @ JRubyMethod ( omit = true ) public IRubyObject backtrace_locations ( ThreadContext context ) { } @ JRubyMethod ( name = "exception" , optional = 1 , rest = true , meta = true ) public static IRubyObject exception ( ThreadContext context , IRubyObject recv , IRubyObject [ ] args , Block block ) { } @ JRubyMethod ( optional = 1 ) public RubyException exception ( IRubyObject [ ] args ) { } @ JRubyMethod ( name = "to_s" ) public IRubyObject to_s ( ThreadContext context ) { } @ Deprecated public IRubyObject to_s19 ( ThreadContext context ) { } @ JRubyMethod ( name = "message" ) public IRubyObject message ( ThreadContext context ) { } @ JRubyMethod ( name = "inspect" ) public IRubyObject inspect ( ThreadContext context ) { } @ JRubyMethod ( name = "==" ) @ Override public IRubyObject op_equal ( ThreadContext context , IRubyObject other ) { } @ JRubyMethod ( name = "===" , meta = true ) public static IRubyObject op_eqq ( ThreadContext context , IRubyObject recv , IRubyObject other ) { } @ JRubyMethod ( name = "cause" ) public IRubyObject cause ( ThreadContext context ) { } public void setCause ( IRubyObject cause ) { } public Object getCause ( ) { } public void setBacktraceData ( BacktraceData backtraceData ) { } public BacktraceData getBacktraceData ( ) { } public RubyStackTraceElement [ ] getBacktraceElements ( ) { } public void prepareBacktrace ( ThreadContext context , boolean nativeException ) { } public void prepareIntegratedBacktrace ( ThreadContext context , StackTraceElement [ ] javaTrace ) { } public void forceBacktrace ( IRubyObject backtrace ) { } public IRubyObject getBacktrace ( ) { } public void initBacktrace ( ) { } @ Override public void copySpecialInstanceVariables ( IRubyObject clone ) { } public void printBacktrace ( PrintStream errorStream ) { } public void printBacktrace ( PrintStream errorStream , int skip ) { } private void printStackTraceLine ( PrintStream errorStream , IRubyObject stackTraceLine ) { } private boolean isArrayOfStrings ( IRubyObject backtrace ) { } public static ObjectAllocator EXCEPTION_ALLOCATOR = new ObjectAllocator ( ) { @ Override public IRubyObject allocate ( Ruby runtime , RubyClass klass ) { } } ; private static final ObjectMarshal EXCEPTION_MARSHAL = new ObjectMarshal ( ) { @ Override public void marshalTo ( Ruby runtime , Object obj , RubyClass type , MarshalStream marshalStream ) throws IOException { } @ Override public Object unmarshalFrom ( Ruby runtime , RubyClass type , UnmarshalStream unmarshalStream ) throws IOException { } } ; public static RubyClass createExceptionClass ( Ruby runtime ) { } public static RubyException newException ( Ruby runtime , RubyClass excptnClass , String msg ) { } public static IRubyObject newException ( ThreadContext context , RubyClass exceptionClass , IRubyObject message ) { } public IRubyObject getMessage ( ) { } private BacktraceData backtraceData ; private IRubyObject backtrace ; public IRubyObject message ; IRubyObject cause ; public static final int TRACE_HEAD = 8 ; public static final int TRACE_TAIL = 4 ; public static final int TRACE_MAX = ( ( RubyException . TRACE_HEAD ) + ( RubyException . TRACE_TAIL ) ) + 6 ; }

Fix:
throw getRuntime ( ) . newTypeError ( "backtrace<seq2seq4repair_space>must<seq2seq4repair_space>be<seq2seq4repair_space>Array<seq2seq4repair_space>of<seq2seq4repair_space>String" ) ;